PRAGUE/PARIS - US Secretary of State John Kerry and other foreign ministers from the six powers negotiating with Iran on its nuclear program may travel to Vienna soon to join the talks, which have failed so far to produce a deal, diplomats said on Tuesday.

The possible arrival of the ministers ahead of a July 20 deadline for an agreement should not be seen as proof that negotiators from Iran, the United States, Britain, France, Germany, Russia and China are on the cusp of a deal, the diplomats cautioned.

"The ministers can help negotiate an extension of the negotiations, if that's deemed useful, and they could help generate momentum to get a deal by July 20, which remains our goal," a Western close to the talks diplomat told Reuters on condition of anonymity.

"Of course, the ministers could also sign an agreement but we're far from signing anything at the moment," the diplomat added. "There are significant gaps in positions."